Update README.md

Author: ogrisel

README.md

@@ -1,2 +1,9 @@
 # scikit-learn-contrib.github.io
-project webpage
+
+The purpose of this repository is to serve a static HTML file with a link to:
+
+https://github.com/scikit-learn-contrib/scikit-learn-contrib/blob/master/README.md
+
+from https://contrib.scikit-learn.org using GitHub Pages configured under a CNAME DNS entry.
+
+Note: due to constraints related to how GitHub handles [domain verification](https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/verifying-your-custom-domain-for-github-pages#verifying-a-domain-that-is-already-taken) this repo needs to be hosted under the https://github.com/scikit-learn organization instead of the https://github.com/scikit-learn-contrib organization.